In the field of the apparatuses devised for counteracting pollution in large water masses contained in natural pools there are at present used devices termed oxygenators which by pumping bring about the mixing of water with air. These devices can consist of floating turbine pumps which suck water and eject it again into the pool, thus facilitating restoration of equilibrium conditions between the atmospheric oxygen and the oxygen dissolved in the water. However, these devices have proved to be of limited usefulness insofar as they facilitate oxygen diffusion in the superficial water layers only, whilst this diffusion process is not suitable to involve the deeper water layers. There are known other devices acting in the deep water layers (for instance: bubble guns, Limno oxygenators and the like), however, their action is confined to limited pool zones; moreover, they either do not provide for the use of oxygen or do not provide for the undissolved oxygen recovery when this gas is used.